Estimating the economic cost of nurse sensitive adverse events amongst patients in medical and surgical settings

AIMS

To identify the costs associated with nurse sensitive adverse events and the impact of these events on patients' length of stay.

DESIGN

Retrospective cohort study using administrative hospital data.

METHODS

Data were sourced from patient discharge information (N = 5544) from six acute wards within three hospitals (July 2016-October 2017). A retrospective patient record review was undertaken by extracting data from the hospitals' administrative systems on inpatient discharges, length of stay and diagnoses; eleven adverse events sensitive to nurse staffing were identified within the administrative system. A negative binomial regression is employed to assess the impact of nurse sensitive adverse events on length of stay.

RESULTS

Sixteen per cent of the sample (n = 897) had at least one nurse sensitive adverse event during their episode of care. The model revealed when age, gender, admission type and complexity are controlled for, each additional nurse sensitive adverse event experienced by a patient was associated with an increase in the length of stay beyond the national average by 0.48 days (p = .001). Applying this to the daily average cost of inpatient stay per patient (€1456), we estimate the average cost associated with each nurse sensitive adverse event to be €694. Extrapolating this nationally, the economic cost of nurse sensitive adverse events to the health service in Ireland is estimated to be €91.3 million annually.

CONCLUSION

These potentially avoidable events are associated with a significant economic burden to health systems. The estimates provided here can be used to inform and prepare the way for future economic evaluations of nurse staffing initiatives that aim to improve care and safety.

IMPACT

As many of these nurse sensitive adverse events are avoidable, in addition to patient benefits, there is a potential substantial financial return on investment from strategies such as improved nurse staffing that can reduce their occurrence.

A protocol to measure the impact of intentional changes to nurse staffing and skill-mix in medical and surgical wards

AIM

The aim of this research is to measure the impact that planned changes to nurse staffing and skill-mix have on patient, nurse, and organizational outcomes.

BACKGROUND

It has been highlighted that there are several design limitations in studies that explore the relationship between nurse staffing and patient, nurse and organizational outcomes; not least that the vast majority of research in this area emanates from studies that are predominantly observational in design. There are limited studies that measure nurse, patient, organizational, and economic outcomes using a longitudinal design following a planned change in nurse staffing.

DESIGN

The research will employ a longitudinal, multimethod approach to evaluate the impact that planned changes in nurse staffing and skill-mix have on wards in three pilot hospitals.

METHODS

Administrative data collection will take place on a shift-by-shift basis prospectively over a three-year period including the measurement of nursing sensitive outcomes: cross-sectional patient experience data and nurse outcomes (nursing work, job satisfaction, burnout, missed care) will be collected at intervals prior to, during and after the implementation of planned changes in nurse staffing and skill-mix. Data will be analysed using interrupted time-series models, adjusted for key hospital, ward and patient-level factors. An economic costing of the changes will further investigate the resources required for the intervention that can then be aggregated to a national level for future roll-out plans.

DISCUSSION

The study aims to provide evidence on the impact of planned changes to nurse staffing and skill-mix based on a systematic approach using a longitudinal design and to determine the extent to which the approach can be implemented at a national level.

Anti-androgens act jointly in suppressing spiggin concentrations in androgen-primed female three-spined sticklebacks - prediction of combined effects by concentration addition

Increasing attention is being directed at the role played by anti-androgenic chemicals in endocrine disruption of wildlife within the aquatic environment. The co-occurrence of multiple contaminants with anti-androgenic activity highlights a need for the predictive assessment of combined effects, but information about anti-androgen mixture effects on wildlife is lacking. This study evaluated the suitability of the androgenised female stickleback screen (AFSS), in which inhibition of androgen-induced spiggin production provides a quantitative assessment of anti-androgenic activity, for predicting the effect of a four component mixture of anti-androgens. The anti-androgenic activity of four known anti-androgens (vinclozolin, fenitrothion, flutamide, linuron) was evaluated from individual concentration-response data and used to design a mixture containing each chemical at equipotent concentrations. Across a 100-fold concentration range, a concentration addition approach was used to predict the response of fish to the mixture. Two studies were conducted independently at each of two laboratories. By using a novel method to adjust for differences between nominal and measured concentrations, good agreement was obtained between the actual outcome of the mixture exposure and the predicted outcome. This demonstrated for the first time that androgen receptor antagonists act in concert in an additive fashion in fish and that existing mixture methodology is effective in predicting the outcome, based on concentration-response data for individual chemicals. The sensitivity range of the AFSS assay lies within the range of anti-androgenicity reported in rivers across many locations internationally. The approach taken in our study lays the foundations for understanding how androgen receptor antagonists work together in fish and is essential in informing risk assessment methods for complex anti-androgenic mixtures in the aquatic environment.

Out-of-season production of 17,20β-dihydroxypregn-4-en-3-one in the roach Rutilus rutilus

In this study, although the highest production of two physiologically significant progestins in teleosts [17,20β-dihydroxypregn-4-en-3-one (17,20β-P) and 17,20β,21-trihydroxypregn-4-en-3-one (17,20β,21-P)] was observed in the period just prior to spawning in both male and female roach Rutilus rutilus, there was also a substantial production (mean levels of 5-10 ng ml(-1) in blood; and a rate of release of 5-20 ng fish(-1)  h(-1) into the water) in males and females in the late summer and early autumn (at least 7 months prior to spawning). During this period, the ovaries were increasing rapidly in size and histological sections were dominated by oocytes in the secondary growth phase [i.e. incorporation of vitellogenin (VTG)]. At the same time, the testes were also increasing rapidly in size and histological sections were dominated by cysts containing mainly spermatogonia type B. Measurements were also made of 11-ketotestosterone (11-KT) in males and 17β-oestradiol and VTG in females. The 3 months with the highest production of 11-KT coincided with the period that spermatozoa were present in the testes. In females, the first sign of a rise in 17β-oestradiol concentrations coincided with the time of the first appearance of yolk globules in the oocytes (in August). The role of the progestins during the late summer and autumn has not been established.

Variation in the reproductive potential of Schistocephalus infected male sticklebacks is associated with 11-ketotestosterone titre

Parasites can impact host reproduction by interfering with host endocrine systems, but the adaptive nature of such effects is disputed. Schistocephalus solidus plerocercoids are parasites of three-spined sticklebacks Gasterosteus aculeatus that are often associated with impaired host reproduction. Here, we relate reproductive behavior and physiology to levels of the androgen 11-ketotestosterone (11KT) in naturally infected and non-infected male sticklebacks from two UK populations. In one population infected males harbored heavy infections and showed uniformly reduced 11KT titres and kidney spiggin (nesting glue protein) content compared to non-infected fish. However in a second population infection levels were more variable and males with smaller infections recorded 11KT and spiggin titres that overlapped those of non-infected fish; among infected males from this population 11KT and kidney spiggin also both correlated negatively with infection severity. Male reproductive behavior correlated closely with 11KT titre in both populations, and infected males with high 11KT levels exhibited normal reproductive behavior. Our results suggest that Schistocephalus infection per se does not block reproductive development in male sticklebacks, and that some male fish may have the ability to breed whilst infected. Our results are not consistent with the hypothesis that Schistocephalus adaptively castrates male hosts via endocrine disruption; rather they support the hypothesis that reproductive disruption is a side effect of the energetic costs of infection.

Synthesis of 17,20beta,21-trihydroxypregn-4-en-3-one by ovaries of reproductively mature Atlantic cod Gadus morhua

Atlantic cod Gadus morhua ovaries were incubated in vitro with tritiated 17-hydroxypregn-4-ene-3,20-dione (17-P) to determine whether 17,20beta-dihydroxypregn-4-en-3-one (17,20beta-P) or 17,20beta, 21-trihydroxypregn-4-en-3-one (17,20beta,21-P), or both, were more likely to be the steroid responsible for inducing oocyte final maturation (i.e. resumption of meiosis). Only 17,20beta,21-P was produced, in addition to 11-deoxycortisol (17,21-P), which is intermediate between 17-P and 17,20beta,21-P. Also, the 5beta-reduced forms of 17-P, 17,21-P and 17,20beta,21-P were all found. Some sulphation of 21-hydroxylated steroids was demonstrated. The ability of female G. morhua to make 17,20beta,21-P but not 17,20beta-P was confirmed by radioimmunoassay of plasma samples from spawning fish. Although small amounts of 17,20beta-P immunoreactivity were detected in a few plasma samples, this was shown, by thin-layer chromatography, to be mostly due to cross-reaction with other unidentified compounds. The evidence strongly suggests that 17,20beta,21-P is more likely than 17,20beta-P to be the maturation-inducing steroid in G. morhua.

The role of the maturation-inducing steroid, 17,20beta-dihydroxypregn-4-en-3-one, in male fishes: a review

The major progestin in teleosts is not progesterone, as in tetrapods, but 17,20beta-dihydroxypregn-4-en-3-one (17,20beta-P) or, in certain species, 17,20beta,21-trihydroxy-pregn-4-en-3-one (17,20beta,21-P). Several functions for 17,20beta-P and 17,20beta,21-P have been proposed (and in some cases proved). These include induction of oocyte final maturation and spermiation (milt production), enhancement of sperm motility (by alteration of the pH and fluidity of the seminal fluid) and acting as a pheromone in male cyprinids. Another important function, initiation of meiosis (the first step in both spermatogenesis and oogenesis), has only very recently been proposed. This is a process that takes place at puberty in all fishes and once a year in repeat spawners. The present review critically examines the evidence to support the proposed functions of 17,20beta-P in males, including listing of the evidence for the presence of 17,20beta-P in the blood plasma of male fishes and discussion of why, in many species, it appears to be absent (or present at low and, in some cases, unvarying concentrations); consideration of the evidence, obtained mainly from in vitro studies, for this steroid being predominantly produced by the testis, for its production being under the control of luteinizing hormone (gonadotrophin II) and, at least in salmonids, for two cell types (Leydig cells and sperm cells) being involved in its synthesis; discussion of the factors involved in the regulation of the switch from androgen to 17,20beta-P production that seems to occur in many species just at the time of spermiation; discussion of the effects of in vivo injection and application of 17,20beta-P (and closely related compounds) in males; a listing of previously published evidence that supports the proposed new function of 17,20beta-P as an initiator of meiosis; finally, discussion of the evidence for environmental endocrine disruption by progestins in fishes.

Further refinement of the non-invasive procedure for measuring steroid production in the male three-spined stickleback Gasterosteus aculeatus

Measurement of steroids that are released into the water via the gills has previously been shown to be an effective way of studying the reproductive endocrinology of the male three-spined stickleback Gasterosteus aculeatus without having to kill the fish. In the present paper, a previous observation on the existence of a compound other than 11-ketotestosterone (11-KT) in water, which cross-reacted in the 11-KT radioimmunoassay was repeated. The amounts of this compound, however, were not sufficient to warrant a separation step prior to carrying out assay. The lack of association between androstenedione levels in water and those in plasma was also confirmed. For the first time, the amounts of testosterone released into the water were shown to be positively correlated with the amounts in plasma, the sampling procedure (placing the fish for 30 min in 50 ml water) had no effect on the rate of release of cortisol but caused a rapid drop in the rate of release of 11-KT (which means that the fish should not be sampled twice in short succession), physical interaction between two nesting males (which was accompanied by aggression) significantly increased the rate of release of 11-KT, androstenedione and testosterone (but not of cortisol) and the rate of release of 11-KT was at its maximum between 2 and 4 h after exposure.

Ethoxyresorufin-O-deethylase (EROD) and vitellogenin (VTG) in flounder (Platichthys flesus): system interaction, crosstalk and implications for monitoring

The extent to which biological systems interact in fish from multi-contaminant areas needs to be understood for full interpretation of monitoring data. This study investigates the interaction between two biomarkers, ethoxyresorufin-O-deethylase (EROD) activity and plasma vitellogenin (VTG) in the European flounder (Platichthys flesus). Flounder were exposed to several waterborne EROD inducers and estrogenic chemicals on their own and in binary combinations. Each experimental exposure was for 10 days. The estrogenic chemicals suppressed PAH-mediated EROD induction. Ethynylestradiol (EE2) and nonylphenol (NP) had threshold concentrations of EROD inhibition similar to those at which they induced VTG production. Estradiol (E2), however, showed an ability to suppress EROD at a concentration much lower than that at which VTG was induced. This established that, although EE2 is a more potent VTG inducer than E2, it is less potent in its ability to inhibit EROD activity. The PAH, dibenz[a,h]anthracene (DbA), showed no effect on the VTG induction caused by EE2 and E2. A small effect was noted with NP at threshold concentrations for VTG induction. Archived data on flounder hepatic EROD activity collected during estuarine monitoring were reassessed in light of the project findings. It is hypothesised that published EROD monitoring data may be an underestimation of effects if it is assumed that estrogen-mediated MFO suppression is occurring in wild populations. A greater understanding of system interaction and other factors, including genetics, that influence biomarker response to contaminants would be required to interpret biomarker monitoring data.

Differential sensitivity of flounder (Platichthys flesus) in response to oestrogenic chemical exposure: an issue for design and interpretation of monitoring and research programmes

This study was conducted as an initial investigation of 'differential response' in one of the main sentinel organisms used for monitoring programmes in United Kingdom estuaries, the flounder Platichthys flesus. It has been hypothesised that monitoring using species with a wide geographical spread and limited migration, such as flounder, might result in the comparison of different genetic stocks and certainly of populations with differing early life stage contaminant exposure histories. Furthermore, it is probable that these pre-exposure and genetic differences could manifest themselves in an ability to respond differently to contaminant exposure, so-called 'differential response'. It is important that the extent and nature of this response is understood, if we want to be able to fully interpret the monitoring data from such programmes. During this study, flounder were collected from four separate sources; wild caught fish from the estuaries of the Rivers Alde, Mersey and Tyne, and farmed flounder from Port Erin Farm, Isle of Man. Under controlled laboratory conditions, groups of fish from each source were exposed to water-borne concentrations of the synthetic oestrogen ethynylestradiol (EE2) at a nominal concentration of 50 ng/l. Plasma was taken from each male fish after 6 and 10 days exposure and analysed for the presence of vitellogenin (VTG) using an ELISA technique. Significant levels of VTG induction were evident in fish from all sources after both 6 and 10 days exposure. Flounder from the Mersey were the only fish with significantly elevated initial background levels of VTG (day 0) and this appeared to be reflected in that these specimens showed the highest induction response after day 6. However, after day 10, fish from all other sites had a slightly higher mean VTG than those from the Mersey which showed significantly (p < 0.05) lower mean plasma VTG. It is suggested that other differential responses may have been masked by the use of a high dose of EE2 which produced maximum induction in nearly all fish. The findings of the study are discussed in terms of implications for further research into the differential response issue and how the initial plasma VTG figures contribute to a time-series from the Mersey, Tyne and Alde estuaries.

Sexually mature male goldfish release large quantities of androstenedione into the water where it functions as a pheromone

Previous studies have demonstrated that ovulatory female goldfish release a variety of sex steroids into the water where they function as a pheromonal blend dominated by C21 steroids that stimulates male hormone release, sperm production and behavior. This study investigated whether male goldfish might also release sex steroids with pheromonal activity. It found that spermiated male goldfish release substantial quantities of androstenedione (AD; about 50 ng/h) together with smaller (10-20 ng/h) quantities of several other related C19 steroids but only very small quantities (<5 ng/h) of C21 steroids. Further, when sexually aroused by females and/or their pheromones, males released even greater quantities of AD (up to 1 microg/h) while C21 steroid release rate changed little. This created a ratio of C19 to C21 steroids of about 50:1 that was dramatically different from that emitted by females (1:7). The male olfactory system was also found to be extremely sensitive to AD, detecting it to near picomolar concentrations. Together with previous studies that have shown water-borne AD to increase male aggressive behavior while suppressing responsiveness to female pheromones, this study establishes AD as a male pheromone in the goldfish. Because ovulating females also release AD but in the presence of C21 steroids, recognition of the male-derived steroid pheromone is presumably mixture dependent.

The potential of the three-spined stickleback (Gasterosteus aculeatus L.) as a combined biomarker for oestrogens and androgens in European waters

The majority of endocrine disruption studies in Europe have been on non-indigenous species (some of them tropical!)--and none of which has traits that make them suitable for the detection of androgenic compounds. To overcome these problems, we have been developing the stickleback as a model biomarker for testing the effect of endocrine disrupters in European waters. Its advantages are: it is the only fish with a quantifiable in vivo androgen and anti-androgen endpoint (the production of the glue protein, spiggin, by the kidney); it is the only fish in which it will be possible to simultaneously test oestrogenic and androgenic properties of compound; it has a genetic sex marker; it is found in all EU countries; it survives and breeds in both seawater and freshwater; it is extremely robust and can be readily deployed in situ; it displays a variety of pronounced reproductive behaviours; it has a simple and short life cycle, low fecundity and high egg/fry survival rates.

Plasma steroids in mature common dentex (Dentex dentex) stimulated with a gonadotropin-releasing hormone agonist

The aim of this study was to identify the major C21 steroids produced in vivo during artificially induced final oocyte maturation and spawning in female common dentex (Dentex dentex). During the spawning season, mature females were treated with a gonadotropin-releasing hormone agonist (GnRHa)-loaded delivery system, with or without pimozide (given as a single dose at the beginning of the experiment). Blood samples were collected at various intervals during the experiment and were assayed for GnRHa, 17,20beta-dihydroxy-4-pregnen-3-one (17,20beta-P), and 17,20beta,21-trihydroxy-4-pregnen-3-one (17,20beta,21-P). A higher percentage of ovulated females was observed in GnRHa-implanted fish, which produced over 10 times more eggs than controls. Relative fecundity was highest in the GnRHa + pimozide group and lowest in controls. The viability of naturally released eggs was low (2 to 15%) in all groups. Plasma concentrations of 17,20beta-P in GnRHa-implanted fish did not increase, but those in control fish decreased, such that there was a significant difference between control and treated fish between 2 and 10 days after treatment. In another experiment, ovulating common dentex were injected intramuscularly with a single dose of 50 microg kg(-1) of GnRHa in saline and were sampled for blood at 0, 3, 6, 12, and 24 h postinjection. A single water sample was taken from the tanks at 9 h postinjection, the tanks having been emptied and refilled at 6 h. Measurements were made of plasma and water concentrations of free and conjugated 17,20beta-P, 17,20beta,21-P, 17beta-oestradiol (E2), and GnRHa (plasma only). The GnRHa injection increased plasma levels of all steroids, with free 17,20beta-P reaching maximal levels within 3 h. GnRHa treatment also increased the amounts of free and conjugated steroids released into the water between 6 and 9 h.

Singlet-triplet splittings and barriers to Wolff rearrangement for carbonyl carbenes

High-level ab initio calculations at the G3(MP2)//B3-LYP level have been used to study carbomethoxychlorocarbene and related halogenocarbenes and carbonyl carbenes. Initial calculations at the more accurate W1' level on the subset CH(2), HCCl, HCF, CCl(2), and CF(2) provide support for the reliability of G3(MP2)//B3-LYP for this type of problem. The W1' calculations also suggest that the experimental S-T splitting is slightly underestimated for HCCl and CF(2) and substantially underestimated for CCl(2), in keeping with other recent high-level studies. Whereas the parent carbonyl carbenes, namely formylcarbene, carbohydroxycarbene, and carbomethoxycarbene, are all predicted to have triplet ground states, their chloro and fluoro derivatives are predicted to have singlet ground states. In particular, carbomethoxychlorocarbene is predicted to have a singlet ground state, with the singlet-triplet splitting estimated as -16.0 kJ mol(-)(1). The barriers to Wolff rearrangement of the singlet carbonyl carbenes generally (but not always) correlate with the exothermicity accompanying the production of ketenes. In the case of the parent carbonyl carbenes, for which the rearrangement reaction is most exothermic, the barriers lie between about 10 and 30 kJ mol(-)(1), whereas for the less exothermic rearrangements of the chloro- and fluoro-substituted carbonyl carbenes, the Wolff rearrangement barriers increase significantly to between 58 and 75 kJ mol(-)(1). The calculated barrier for carbomethoxychlorocarbene is 58.2 kJ mol(-)(1).

Steroid profiles in cultured female jundiá, the Siluridae Rhamdia quelen (Quoy and Gaimard, Pisces Teleostei), during the first reproductive cycle

The jundiá Rhamdia quelen (Quoy and Gaimard) is a teleost species from the Siluridae family and is an important species for aquaculture in temperate and subtropical climates. Gonad and blood tissue samples were taken from cultured jundiá females between 1998 and 1999. Plasma concentrations of 17beta-estradiol (E(2)), testosterone (T), 11-ketotestosterone (11-KT), 17-hydroxy-4-pregnene-3,20-dione (17-P), 17,20beta-dihydroxy-4-pregnen-3-one (17,20beta-P), and 17,20beta,21-trihydroxy-4-pregnen-3-one (20beta-S) were measured by radioimmunoassay and potential correlations with the stage of oogenesis and sexual maturation examined. During the experimental period two spawning episodes were observed. Plasma concentrations of E(2) increased progressively during oocyte development, simultaneously with the appearance of yolk vesicles and increasing amounts of deposited yolk. In female jundiá, the T peak occurred in October and was coincident with the peak in gonadosomatic index. Two distinct peaks of progestogens were detected, corresponding to the two spawning episodes, suggesting that one or more of these steroids might act as the "maturational-inducing steroid" in jundiá. Unusually large amounts of 11-KT were also measured in the plasma of mature jundiá females. The identity of 11-KT was confirmed by thin-layer chromatography. Although the profiles of the other steroids are compatible with the roles proposed for the action of these hormones in other teleosts, the role of 11-KT, normally found only in males, is unknown.

Seasonal variations and maturity stages in relation to differences in serum levels of gonadal steroids, vitellogenin, and thyroid hormones in the common dentex (Dentex dentex)

Seasonal variations in serum concentrations of 17beta-estradiol (E(2)), vitellogenin (Vg), testosterone (T), 11 ketotestosterone (11-KT), and thyroid hormones (T(4), l-thyroxine; and T(3), 3,5, 3'-triiodo-l-thyronine) were investigated during the first, second, and third reproductive cycles in intensively reared populations of common dentex, Dentex dentex, and correlated with gonadal development and spawning. In females, there were baseline E(2) values (<0.10 ng/ml) and negligible Vg concentrations during the postspawning and pregametogenesis period (June to December), and these increased thereafter to peak during the spawning period. Maximum T(3) and T(4) serum concentrations were found around spawning. There was a positive correlation during vitellogenesis and final maturation between Vg and T(3) (r(2) = 0.366). In addition, Vg and T(3) concentrations were statistically higher in the stages of vitellogenesis and final maturation than at the other stages (P<0.001). Minimum T(3) and T(4) concentrations (October) coincided with the decrease in water temperature and the associated decrease in the daily feeding rate and the specific growth rate. In males, as in females, seasonal changes in serum levels of T and 11-KT were well correlated with gonadal development. The presence of males in the stage of completed spermiogenesis in December coincided with the surge in both androgens and this increase lasted until the end of the spawning period. There were no significant differences in serum T(3) and T(4) levels among the maturity stages. The observed seasonal changes in serum gonadal steroids and Vg reflected the pattern of oocyte development and the spawning behavior of common dentex and were typical of the patterns described in most multiple spawners studied to date. Thyroid hormones may enhance early ovarian development and stimulate vitellogenesis in female dentex.

Plasma-sulfated C21-steroids increase during the periovulatory period in female common wolffish and are influenced by temperature during vitellogenesis

Plasma concentrations of steroids during the periovulatory period were measured in female common wolffish reared at three different temperatures. Steroids were quantified by radioimmunoassay (RIA). Two "broad-spectrum specificity" RIAs-one which detects C21-steroids with a 17,20beta-dihydroxyl configuration (17,20beta-steroids) and the other which detects C21-steroids with a 5beta-reduced, 3alpha-hydroxyl configuration (5beta,3alpha-steroids)-picked up very large amounts of cross-reacting material (1.7 microg ml(-1) in one fish) in the sulfate fraction of plasma from ovulating females. Reverse-phase high-performance liquid chromatography and thin-layer chromatography revealed two major steroids: 5beta-pregnane-3alpha,17,20beta-triol (80%) and 5beta-pregnane-3beta,17,20beta-triol (20%). The sulfated forms of these steroids were elevated 4 to 6 days before and during ovulation, compared with those of females in vitellogenic and postspawning condition, in which concentrations were below 2.0 ng ml(-1). In the three groups of fish held at 4, 8, and 12 degrees C during vitellogenesis, but returned to 4 degrees C just prior to the spawning season, the mean concentrations of sulfated 17,20beta-steroids in ovulating females were 530, 635, and 325 ng ml(-1), respectively. The corresponding concentrations of free 17,20beta-dihydroxy-4-pregnen-3-one (17,20beta-P; the maturation-inducing steroid in many teleosts) were 0.88, 0.86, and 0.57 ng ml(-1), respectively. Only minute amounts of 17,20beta,21-P and its sulfated derivatives were detected. Significantly lower steroid concentrations in the 12 degrees C group indicate that steroid synthesis and/or metabolism during the periovulatory period are influenced by the temperature experienced during vitellogenesis. In male fish, plasma concentrations of both sulfated 17,20beta-steroids and free 17,20beta-P were low (< 2.0 ng ml(-1)) at all times.

Circulating C-21 steroids in relation to reproductive condition of a viviparous marine teleost, Sebastes rastrelliger (grass rockfish)

Plasma concentrations of free, glucuronidated, and sulfated steroids were measured in grass rockfish (Sebastes rastrelliger) at identified stages of ovarian development and pregnancy using radioimmunoassays validated for the detection of individual steroids or compounds with a particular configuration. Changes in reproductive status were most clearly reflected in concentrations of free C-21 steroids. Previtellogenic, vitellogenic, and postspawn fish exhibited uniformly low concentrations of circulating C-21 steroids while pregnant fish showed a pronounced and significant increase in a series of free 17,20beta-dihydroxylated steroids together with 17,20alpha-P. Among individual steroids, the compound exhibiting the greatest fluctuation in relation to reproductive condition was 17,20beta-P-5beta, which during pregnancy showed a 22-fold increase from basal concentrations. Smaller relative increases in association with pregnancy were also seen in 17, 20beta-P, 17,20beta,21-P, and 17,20alpha-P (3.5-, 3.5-, and 5.5-fold increases, respectively). Fish in the final stages of pregnancy or which had recently spawned exhibited uniformly low concentrations of the C-21 steroids, indicating a drop in circulating amounts of these compounds around the time of parturition. The hormone profiles established during the annual reproductive cycle of the grass rockfish suggest that C-21 steroids may contribute to the endocrine mechanisms which regulate viviparity in this highly fecund marine teleost. The C-21 steroids characterized in this study may provide appropriate reference compounds in the future evaluation of this concept.

The extent of oestrogenic contamination in the UK estuarine and marine environments--further surveys of flounder

In 1996, The Centre for Environment, Fisheries and Aquaculture Science (CEFAS) initiated a project to establish whether oestrogenic materials are present in UK estuarine and marine waters at biologically significant concentrations, and to investigate some of the possible effects which these may have in flounder (Platichthys flesus). Early results are published elsewhere; this paper describes the results of a second wider survey of vitellogenin and reproductive abnormalities in UK flounder. Vitellogenin levels in male blood plasma in the period from spring to winter 1997 were found to be significantly elevated (in comparison with a clean reference site on the Alde estuary) in at least one sample from most of the 11 estuaries investigated. The exceptions were the Tamar and the Dee where all fish appeared entirely normal. In broad terms, the degree of oestrogenic contamination as measured by male vitellogenesis in the various estuaries was ranked in the following descending order: Tees > Mersey > Tyne > Wear = Humber = Clyde = Southampton Water = Thames > Dee = Tamar. VTG concentrations in Tees, Mersey and Tyne male fish were extremely high (> 100,000 ng/ml), and often exceeded those normally found in sexually mature females. At most locations, ovotestis conditions in male flounder were entirely absent but 9% of male Mersey fish and 7% of male Tyne fish contained ovotestis. In a few cases, eggs were fully developed with yolk granules. Most testes did not show gross morphological abnormalities related to oestrogenic exposure, although one testis from a Mersey fish appeared to be almost entirely composed of eggs. Abnormal sex ratios were not seen in any estuary. The paper concludes by outlining a new research programme which will be addressing the biological significance of these observations.

Gonadotrophin-releasing hormone agonist stimulates milt fluidity and plasma concentrations of 17,20beta-dihydroxylated and 5beta-reduced, 3alpha-hydroxylated C21 steroids in male plaice (Pleuronectes platessa)

Spermiating male plaice were caught in the North Sea and acclimatised to laboratory conditions. In two experiments, males were injected intramuscularly with either microspheres or pellets containing gonadotrophin-releasing hormone agonist (GnRHa). Blood was sampled at 2- to 5-day intervals. Individual blood plasma specimens were assayed for testosterone, 5beta-reduced, 3alpha-hydroxy ("5beta,3alpha") steroids and sulphated 17, 20beta-dihydroxy ("17,20beta") steroids. Pooled plasma samples were also assayed for free and sulphated 17, 20beta-dihydroxy-4-pregnen-3-one, free 11-ketotestosterone, and glucuronidated testosterone and 11-ketotestosterone. Plasma concentrations of all steroids were significantly elevated by GnRHa from 2 to 5 days onwards following treatment. The most marked changes occurred in the concentrations of the sulphated 17,20beta steroids, which comprised approximately equal amounts of 5beta-pregnane-3alpha,17,20beta-triol 20-sulphate (3alpha,17, 20beta-P-5beta-S) and 5beta-pregnane-3beta,17,20beta-triol 20-sulphate, rising from ca. 1 to 30-80 ng/ml in the first and from ca. 8 to 80 ng/ml in the second experiment. Concentrations of 5beta, 3alpha steroids matched those of 17,20beta steroids in one experiment. However, in the other experiment, the two RIAs yielded highly disparate results in about 50% of the fish (including males in the control group). The plasma of these fish contained excessive amounts of 5beta,3alpha-immunoreactive material between 10 and 25 days. This material was identified as 3alpha,17, 21-trihydroxy-5beta-pregnan-20-one 21-sulphate (a metabolite of 11-deoxycortisol). All previous studies have indicated that when plasma concentrations of this steroid are high, so are those of 3alpha,17,20beta-P-5beta-S. This is the first indication that these steroids are regulated independently. In a third experiment, milt fluidity and production were assessed at 10, 15, and 25 days following GnRHa implantation. Milt volume and fluidity were significantly enhanced by the GnRHa treatment.

Plasma gonadotropin II, sex steroids, and thyroid hormones in wild striped bass (Morone saxatilis) during spermiation and final oocyte maturation

The blood levels of gonadotropin II (GtH II), sex-steroid hormones, and thyroid hormones were determined in wild spermiating male striped bass (Morone saxatilis) in males and in females at various stages of final oocyte maturation (FOM), captured on their spawning grounds. The progression of spermiation was associated with increases in plasma GtH II and decreases in plasma testosterone (T), 11-ketotestosterone, and thyroxine (T4). Plasma triiodothyronine (T3) remained at high and relatively unchanged levels. Plasma levels of 17,20beta-dihydroxy-4-pregnen-3-one (17,20beta-P) and 17,20beta, 21-trihydroxy-4-pregnen-3-one (17,20beta,21-P), the proposed maturation-inducing steroids (MIS) in striped bass, were low and unchanged during the same period. It was concluded that low progestogen levels are adequate to induce spermiation in striped bass, and that higher levels may be associated with spawning behavior. In the females, based on the profiles of the studied hormones, FOM was separated into two phases. Early FOM, which included germinal vesicle (GV) migration and lipid-droplet coalescence, was associated with elevations in plasma GtH II, T, and estradiol 17beta. Late FOM, which included GV breakdown and yolk-globule coalescence, was associated with a further surge in plasma GtH II, increases in the levels of the two MIS, mainly 17, 20beta-P, and a drop in T4. Plasma T3 levels did not change during FOM. Examination of conjugated steroids demonstrated, in the males, a reduction in conjugated androgens at the peak of the spawning season and, in the females, a small increase in conjugated 17, 20beta-dihydroxylated and 5beta-reduced,3alpha-hydroxylated steroids after spawning. This is the most comprehensive report, to date, on the endocrine regulation of gonadal maturation in wild striped bass, demonstrating that a two-stage process of FOM is regulated by different endocrine signals, providing further evidence for the involvement of 17,20beta-P as a MIS in the females, and indicating that both males and females are in an euthyroid state during the spawning season.

Changes in plasma gonadotropin II and sex steroid hormones, and sperm production of striped bass after treatment with controlled-release gonadotropin-releasing hormone agonist-delivery systems

Spermiating striped bass, a perciform fish, were treated with two controlled-release gonadotropin-releasing hormone agonist (GnRHa)-delivery systems, and the resulting changes in plasma gonadotropin II (GTH II), testosterone (T), 11-ketotestosterone (11-KT), 17,20beta-dihydroxy-4-pregnen-3-one (17,20beta-P), and 17,20beta,21-trihydroxy-4-pregnen-3-one (17,20beta,21-P) were correlated with changes in milt production and sperm density. GnRHa-delivery systems induced a sustained elevation of plasma GnRHa and GTH II for 14 days. Plasma T levels were unchanged after GnRHa treatment, while 11-KT levels increased significantly. Plasma 17,20beta-P also increased after GnRHa treatment and remained elevated compared to levels in controls, while plasma 17,20beta,21-P levels were unaffected. Both GnRHa-delivery systems induced many-fold increases in total expressible milt, lasting throughout the 14 days of the study. Sperm density decreased 2 days after GnRHa treatment, with a subsequent increase by Day 7. This study demonstrates that GnRHa-delivery systems induce a sustained elevation of plasma GTH II levels in striped bass, resulting in a long-term enhancement of milt production. The endocrine changes observed suggest that 11-KT and 17,20beta-P, but not 17,20beta,21 -P, are mediating the effects of GTH II on spermiation.

Pheromone-induced spawning of Pacific herring. II. Plasma steroids distinctive to fish responsive to spawning pheromone

A spawning pheromone in the milt (semen) and testes of the Pacific herring, Clupea harengus pallasi, is thought to facilitate school spawning of this species. We found that responsiveness to the spawning pheromone was variable among ripe fish (milt-producing or ovulated). Measurement of five principle reproductive steroids in the free form and five steroids in conjugated forms in the plasma of male fish early in the spawning season (newly ripe fish) showed that elevated plasma levels of 3 alpha, 17 alpha-dihydroxy-3 beta-pregnan-20-one and 17 alpha-hydroxyprogesterone coincided with responsiveness to the spawning pheromone in these fish; levels of other steroids did not differ. In contrast, responsiveness to the pheromone by female fish later in the spawning season (ripe-and-holding fish) coincided with lower levels of glucuronated 17 alpha,20 beta-dihydroxyprogesterone and a lower gonadosomatic index. We suggest that these differences indicate a more advanced mature reproductive state in the responsive individuals among both the newly ripe male and the ripe-and-holding female fish. We found no differences in the level of cortisol in the blood of the herring that could be correlated with differences in pheromonal responsiveness. We conclude that differences in responsiveness to the spawning pheromone coincide to some extent with levels of reproductive maturation but probably not with recent stress.

Use of a radioimmunoassay which detects C21 steroids with a 17, 20beta-dihydroxyl configuration to identify and measure steroids involved in final oocyte maturation in female plaice (Pleuronectes platessa)

A radioimmunoassay (RIA) has been developed to detect a range of C21 (pregnane) steroids with a 17,20beta-dihydroxyl (17,20beta) configuration. In conjunction with reverse-phase high-performance liquid chromatography (HPLC), it identifies and quantifies the metabolites of 17,20beta-dihydroxy-4-pregnen-3-one, the putative "maturation-inducing steroid" in female plaice Pleuronectes platessa. Total levels of 17,20beta metabolites which can be extracted from plasma or urine with diethyl ether (i.e., free steroids) are very low (<3 ng/ml). However, total levels of 17,20beta metabolites which can be released by solvolysis (i.e., sulphated steroids) are very high (up to 1 microg/ml in plasma and 10 microg/ml in urine). On HPLC, these sulphated metabolites have been identified (in order of abundance in plasma) as: 5beta-pregnane-3alpha,17,20beta-triol, 5beta-pregnane-3beta,17,20beta-triol, 17, 20beta-dihydroxy-4-pregnen-3-one, and 17, 20beta-dihydroxy-5beta-pregnan-3-one. These steroids are absent from plasmas of fish which have not yet begun final oocyte maturation. The results support the hypothesis that 17, 20beta-dihydroxy-4-pregnen-3-one is the maturation-inducing steroid in plaice but that it is rapidly metabolised to render it inactive. The results also show that the '17,20beta'-RIA, in combination with an overnight acid solvolysis procedure, is a useful procedure for monitoring the effects of exogenous factors (such as gonadotrophin injections) on final oocyte maturation in female plaice.

17α, 20β-dihydroxy-4-pregnen-3-one 20-sulphate is a potent odorant in precocious male Atlantic salmon ( Salmo salar L. ) parr which have been pre-exposed to the urine of ovulated females

Electrophysiological recordings from the olfactory epithelium have shown that 17 alpha,20 beta-dihydroxy-4-pregnen-3-one 20-sulphate (17,20 beta-P-sulphate; a conjugate of the oocyte-maturation-inducing steroid in teleosts) is a potent odorant in precocious male Atlantic salmon (Salmo salar L.) parr. However, the olfactory epithelium of these fish only appeared to be responsive to the steroid after stimulation with the urine of ovulated female Atlantic salmon. Immature fish did not respond at any time. Stimulation with urine from immature and precocious male Atlantic salmon parr did not make the olfactory epithelium of precocious male salmon parr responsive to the steroid. 17,20 beta-P-sulphate was found in the urines of ovulated females, precocious male parr and mature male Atlantic salmon. The findings are discussed in relation to the possible role of 17,20 beta-P-sulphate in the physiology of Atlantic salmon.

Use of a radioimmunoassay which detects C21 steroids with a 5beta-reduced, 3alpha-hydroxylated configuration to identify and measure steroids involved in final oocyte maturation in female plaice (Pleuronectes platessa)

Two radioimmunoassays (RIAs) have been developed which detect C21 (pregnane) steroids with a 5beta-reduced, 3alpha-hydroxyl (5beta, 3alpha) configuration. One RIA only detects 3alpha,17, 21-trihydroxy-5beta-pregnan-20-one and 3alpha, 17-dihydroxy-5beta-pregnan-20-one, whilst the other detects a range of 5beta,3alpha steroids, including 5beta-pregnane-3alpha,17,20 beta-triol, a major metabolite of 17, 20beta-dihydroxy-4-pregnen-3-one, the putative oocyte maturation-inducing steroid in plaice Pleuronectes platessa. The RIAs, in conjunction with reverse-phase high-performance liquid chromatography (HPLC), have identified and quantified the steroids in plasma and urine of reproductively mature females. Total levels of 5beta,3alpha metabolites which can be extracted with diethyl ether (i.e., free steroids) are relatively low (<10 ng/ml). However, total levels of 5beta,3alpha metabolites released by solvolysis (i.e. , sulphated steroids) are very high (up to 1000 ng/ml in plasma and 20 microg/ml in urine). On HPLC, these metabolites have been identified (in order of their abundance in plasma) as: 3alpha,17, 21-trihydroxy-5beta-pregnan-20-one, 5beta-pregnane-3alpha,17, 20beta-triol, 5beta-pregnane-3alpha,17,20alpha-triol, 3alpha,11beta, 17,21-tetrahydroxy-5beta-pregnane-20-one, and 3alpha, 17-dihydroxy-5beta-pregnan-20-one. Levels of the first three steroids are significantly elevated in female plaice undergoing natural or gonadotrophin-induced final oocyte maturation.

Extragonadal production of 17,20-dihydroxy-4-pregnen-3-ones in vitro in cyprinid fish

Muscle, heart, eye, testis, blood, and sperm of trout and goldfish have been examined for the presence of 20-hydroxysteroid dehydrogenase by incubation with [3H]17-hydroxyprogesterone in the presence of 0, 0.1, 1, or 10 micrograms/ml of unlabeled substrate. In trout, 17-hydroxyprogesterone was metabolized only by sperm and testis, with 17,20 beta-dihydroxy-4-pregnen-3-one (17,20 beta P) as the major product and traces (< 2%) of 17,20 alpha-dihydroxy-4-pregnen-3-one (17,20 alpha P). In goldfish, maximum conversion of 17-hydroxyprogesterone to 17,20 alpha P was over 30% per 100 mg tissue in eyeball, heart, and testis, 12% per 20 microliters blood, and 18% per 20 microliters sperm, but less than 5% per 100 mg muscle. 17,20 alpha P was the only metabolite of 17-hydroxyprogesterone in all incubations of nongonadal tissue in goldfish. Within the cyprinid eye, there was no significant activity in the lens, the fluids, or the retina. The possible relationship between the teleost 20 alpha- and 20 beta-hydroxysteroid dehydrogenases, the mammalian 20-hydroxysteroid dehydrogenases, and members of the aldo-keto reductase and short-chain dehydrogenase superfamilies is discussed.

Reproductive steroids during maturation in a primitive teleost, the Pacific herring (Clupea harengus pallasi)

Concentrations of reproductive steroids were measured in the plasma of captive Pacific herring, Clupea harengus pallasi, (1) prior to ovulation and milt production, (2) during the periovulatory and newly milt-producing period, (3) during a "ripe" holding period after ovulation and during milt production, and (4) before and after spawning. 17alpha,20beta-Dihydroxyprogesterone (17,20beta-P), despite being present only in low concentrations in the unconjugated (free) form (<10 ng/ml), is likely to be the maturation inducing steroid in females and was associated with the initiation of milt production in males since its levels are elevated coincidentally with these events. Glucuronated 17,20beta-P, free 17alpha-hydroxyprogesterone (17-P), and free and glucuronated 3alpha, 17alpha-dihydroxy-5beta-pregnan-20-one (3alpha,17-P-5beta) were present in high concentrations (140-250 ng/ml) in periovulatory females and newly milt-producing males. This steroid pattern suggests that the low levels of 17,20beta-P are due to glucuronation and competitive conversion of its precursor, 17-P, to free and glucuronated 3alpha, 17-P-5beta. Glucuronated testosterone was the principal steroid in preovulatory and premilt-producing fish (200-350 ng/ml), coincident with similar levels of glucuronated 11-ketotestosterone in males. After ovulation females did not spawn synchronously until 2 months later, which may be partially due to reduced environmental cues in the captive situation, while male fish released milt sporadically throughout the ripe holding period. Steroidal indicators of readiness to spawn in females or males were not detected. Rather, levels of all steroids gradually decreased in ripe holding fish (<30 ng/ml) to reach even lower levels (<1 ng/ml) after spawning. We suggest that "runniness" of gametes is a distinctive characteristic of females that are ready to spawn, but that this may result from relaxation of sphincter muscles rather than being an additional maturational step.

Milt and endocrine responses of mature male Atlantic salmon (Salmo salar L.) parr to water-borne testosterone, 17,20 beta-dihydroxy-4-pregnen-3-one 20-sulfate, and the urines from adult female and male salmon

Mature male Atlantic salmon (Salmo salar L.) parr responded to the urine from ovulated females with significant increases in plasma gonadotropin II, 17,20 beta-dihydroxy-4-pregnen-3-one, testosterone, and 11-ketotestosterone concentrations and volumes of expressible milt. There were also significant increases in biliary free steroid and steroid conjugate concentrations. Urine from mature adult male salmon also affected male parr, which responded with increased plasma gonadotropin II concentrations and expressible milt. However, male urine did not elevate the plasma and bile concentrations of any of the steroids. When two of the three known steroids which are detected by the mature male salmon parr olfactory epithelium were tested for priming activity, results showed that these compounds had little or no activity when added to the water. Only plasma gonadotropin II concentrations increased in mature male parr exposed to 17,20 beta-dihydroxy-4-pregnen-3-one 20-sulfate. Female and mature adult male urines contain at least one priming pheromone and there was no conclusive evidence for this priming pheromone being one of the tested steroids. However, the fact that water-borne 17,20 beta-dihydroxy-4-pregnen-3-one 20-sulfate can have a physiological effect in male parr suggests that it may have a role as one of a mixture of compounds in female urine that males detect and respond to. The lack of a priming-like effect of testosterone supports a previous hypothesis that the major pheromonal role of this steroid is as an attractant for mature male salmon parr.

Gonadotropins I and II do not stimulate thein vitro secretion of 17α,20β-dihydroxy-4-pregnen-3-one 20-sulphate by rainbow trout gonads during final sexual maturation

Thein vitro secretion of 17α,20β-dihydroxy-4-pregnen-3-one 20-sulphate (17α,20β-P-sulphate) and the free steroid 17α,20β-dihydroxy-4-pregnen-3-one (17α,20β-P), by rainbow trout (Oncorhynchus mykiss) gonads, in response to gonadotropin (GTH) I and GTH II, were studied during the final stages of sexual maturation. Substantial amounts of 17α,20β-P-sulphate were produced, by both mature ovaries and testes, indicating considerable 20β-hydroxysteroid sulphotransferase (20β-HST) activity within these tissues. In the post-ovulatory ovary the level of 17α,20β-P-sulphate (36.6 ng ml(-1)) greatly exceeded that of 17α,20β-P (8.59 ng ml(-1)). The amount of 17α,20β-P-sulphate produced in incubations of both mature ovary and testes was unaffected by either GTH I or GTH II treatment at physiological concentrations up to 100 ng ml(-1). Similarly, incubations of maturing ovary and testes, treated with GTH I or GTH II, in the presence of added 17α,20β-P at 100 ng ml(-1) of medium, produced levels of 17α,20β-P-sulphate that were similar to those of the controls. In incubations of mature ovarian follicles at the stages of germinal vesicle breakdown and preovulation, both GTHs significantly stimulated secretion of 17α,20β-P, although GTH II was always more potent than GTH I. GTH II significantly elevated the levels of 17α,20β-P in testicular incubations from mature males more than 4-fold relative to GTH I and controls, which did not differ from one another.In conclusion, 20β-HST, the enzyme responsible for the sulphate conjugation of 17α,20β-P, was found to be active in the ovaries and testes of rainbow troutin vitro. However, the levels of this enzyme do not appear to be regulated by either GTH I or GTH II.

Excretion of free and conjugated steroids in rainbow trout (Oncorhynchus mykiss): evidence for branchial excretion of the maturation-inducing steroid, 17,20 beta-dihydroxy-4-pregnen-3-one

The goal of this study was to identify excretory routes of three main steroids produced by sexually mature male and female rainbow trout: 17,20 beta-dihydroxy-4-pregnen-3-one (17,20 beta-P), sulfated 17,20 beta-P (17,20 beta-P-S), and testosterone glucuronide (TG). Spermiating males or maturing trout were cannulated via the dorsal aorta and urinary bladder and injected with tritiated steroids. Blood, water, and urine were sampled over the next 12 hr when the fish were killed and bile was collected. The identities of the excreted products were determined by anion-exchange chromatography, reverse-phase high-performance liquid chromatography, enzyme hydrolysis, acid solvolysis, microchemical modification, and thin-layer chromatography. Following the injection of tritiated 17,20 beta-P, 25% of the radioactivity rapidly appeared unmodified in the water; 15% appeared slowly in the urine, mainly as 17,20 beta-P-S; and 40% was recovered in the bile, mainly as 17,20 beta-P-glucuronide. 17,20 beta-P was shown to be released into the water via the gills. Over the 12-hr sampling period, 20% of the 17,20 beta-P released into the water was taken up again by the fish (also branchially). A mathematical analysis showed that 40% of the 17,20 beta-P would have been released into the water in the absence of uptake. Following the injection of tritiated 17,20 beta-P-S, 63% appeared very rapidly, in an unmodified form, in the urine, and 15% was recovered in the bile. Following the injection of tritiated TG, 9% appeared slowly, mainly untransformed, in the urine, and 59% was recovered in the bile. These results show that the three types of steroids are released into the water by three different routes: free steroids, gills; sulfated steroids, urine; and glucuronidated steroids, bile.

Sulfated 17,20 beta-dihydroxy-4-pregnen-3-one functions as a potent and specific olfactory stimulant with pheromonal actions in the goldfish

This study demonstrates that in addition to using the maturational steroid hormone 17,20 beta-dihydroxy-4-pregnen-3-one (17,20 beta-P) as a potent sex pheromone, the goldfish uses its sulfated metabolite 17,20 beta-dihydroxy-4-pregnen-3-one 20-sulfate (17,20 beta-P-20S). As measured by electro-olfactogram recording (EOG), the goldfish olfactory epithelium is extremely sensitive to both free and sulfated 17,20 beta-P (detection thresholds of approximately 10(-12) and 10(-11) M) but not to glucuronidated or phosphated 17,20 beta-P. Furthermore, both structure-activity and cross-adaptation studies using EOG indicated that 17,20 beta-P-20S and 17,20 beta-P are detected by different olfactory receptor sites, suggesting that these cues function as a distinguishable mixture. Finally, although the pheromonal activity of 17,20 beta-P-20S appears to be slightly less than that of 17,20 beta-P, it too stimulates gonadotropin release and sperm production in male goldfish. The precise function of 17,20 beta-P-20S remains somewhat enigmatic, however, because it does not appear to enhance the actions of 17,20 beta-P and is released by a different mechanism. In any case, our findings clearly establish that a fish olfactory system can detect particular conjugated steroidal compounds in a highly specific manner and that naturally released conjugated steroids can function as components of a pheromonal mixture.

Sulfation and uptake of the maturation-inducing steroid, 17α,20β-dihydroxy-4-pregnen-3-one by rainbow trout ovarian follicles

Rainbow trout ovarian follicles were incubated in vitro with tritiated 17α,20β-dihydroxy-4-pregnen-3-one (17,20β-P; maturation-inducing steroid). Within 18-24 h, 56-66% had been converted to tritiated 17α,20β-dihydroxy-4-pregnen-3-one 20-sulfate (identification confirmed by HPLC) and 27% had been taken up (absorbed) by the follicles. Addition of 125 ng of cold (non-tritiated) 17,20β-P to the incubations caused a decrease in the percentage of [(3)H]-17,20β-P which was sulfated (56% → 10%) and an increase in the percentage that was taken up (27% → 57%). Seven steroids were tested for their effectiveness in decreasing the sulfation and increasing the uptake of tritiated [(3)H]-17,20β-P. The order of effectiveness was in both cases the same: 17,20β-P > cortisol > 11-deoxycortisol > 17α,20β,21-trihydroxy-4-pregnen-3-one > 17α-hydroxy-4-pregnene-3,20-dione > 17β-estradiol > testosterone. This indicated that the processes of sulfation and uptake of [(3)H]-17,20β-P were related to each other and led to the hypothesis that, when cold 17,20β-P is added to the medium, it reduces the proportion of [(3)H]-17,20β-P which is sulfated and thus allows more free [(3)H]-17,20β-P to enter the ovarian follicles. This hypothesis was supported by the finding that each ovarian follicle had the capacity in vitro to sulfate only ca. 2 ng of [(3)H]-17,20β-P per 18h but a capacity to take up > 500 ng per 18h.Gonadotropin I, Gonadotropin II, forskolin and phorbol-12-myristate-13-acetate (which all have an affect on steroid biosynthesis) did not affect the amount of 17,20β-P which was sulfated. Sulfating activity was localized in the thecal cell layer of the follicle. The yolk fraction was shown to be responsible for absorbing the [(3)H]-17,20β-P.

Ab initio Predictions of the Gas-Phase Acidities of Diazirine and Diazomethane

Absolute gas-phase acidities of diazirine, diazomethane, dimethylamine, ethylamine and methylamine have been obtained with ab initio molecular orbital calculations at the G2 and G2(MP2) levels of theory. Values at the G2 and G2(MP2) levels are all within 1 kJ mol-1 of one another. The calculated gas-phase acidities for diazomethane, dimethylamine, ethylamine and methylamine (and other reference molecules considered) are all within 3 kJ mol-1 of experiment. For diazirine the calculated result, although consistent with experiment, would suggest an acidity towards the lower end of the range of possible experimental values.

Time course of release of pheromonally active gonadal steroids and their conjugates by ovulatory goldfish

Previous studies have demonstrated that ovulatory goldfish synthesize and release a variety of steroids into the water, where some of them function as sex pheromones. Among the steroids which have been measured are free androstenedione, testosterone, 17 alpha,20 beta-dihydroxy-4-pregnen-3-one (17,20 beta-P), 17 alpha,20 beta,21-trihydroxy-4-pregnen-3-one (17,20 beta,21-P), 17 alpha-hydroxy-4-pregnene-3,20-dione (17-P), 11-deoxycortisol (17,21-P), and 17 alpha,20 alpha-dihydroxy-4-pregnen-3-one (17,20 alpha-P), glucuronidated testosterone, 17,20 beta-P, and 17,20 beta,21-P, and sulfated 17,21-P, 17,20 beta-P, and 17,20 beta,21-P. This study reports the changes in the amounts of these steroids released into the water, at 3-hr intervals, by 12 female goldfish injected with human chorionic gonadotrophin (HCG). Eight fish ovulated. The amounts of steroids released into the water were significantly higher in the fish which ovulated than in those which did not. The peak rate of release (ng per hour) of free androstenedione (91), glucuronidated testosterone (143), and sulfated 17,21-P (33) occurred at ca. 4 hr postinjection; free 17-P (163) and free 17,21-P (217) at ca. 6 hr.; free 17,20 beta-P (58) and free 17,20 beta,21-P (58) at ca. 7.5 hr; and glucuronidated 17,20 beta-P (96), glucuronidated 17,20 beta,21-P (264), sulfated 17,20 beta-P (64) and sulfated 17,20 beta,21-P (153) at ca. 9 hr. Amounts of all of the steroids were at their lowest between 12 and 15 hr and, in the ovulated fish, had risen significantly again between 18 and 21 hr. The amounts of glucuronidated testosterone, 17,20 beta-P and 17,20 beta,21-P, and of sulfated 17,20 beta-P and 17,20 beta,21-P, in water exceeded those of free steroid. Elevated levels of free and glucuronidated steroids were also found in the blood plasma of HCG-injected fish. Considerably more androstenedione than testosterone was released into the water. Assessment of the "pheromonal effectiveness" of each steroid indicated that the free and sulfated forms of 17,20 beta-P and 17,20 beta,21-P, and androstenedione were the most important pheromonal steroids released by female goldfish.

The evolution of hormonal sex pheromones in teleost fish: poor correlation between the pattern of steroid release by goldfish and olfactory sensitivity suggests that these cues evolved as a result of chemical spying rather than signal specialization

It is becoming increasingly evident that many teleost fish use hormones and their metabolites as sex pheromones. Although hormonal pheromone systems of several species of fish have now been characterized, that of the goldfish is the best understood. Reproductively-active female goldfish sequentially release derivatives of three steroidal hormones and two prostaglandins which have specific and potent actions on the goldfish olfactory sense and subsequently conspecific reproductive behaviour and physiology. Three goldfish hormonal pheromones are unmodified sex hormones which are also found in the blood of many other species of fish and are therefore unlikely to be species-specific. This scenario evokes two related questions. First, how did these systems evolve? Second, do hormonal pheromones represent specialized signals used for communication or rather simple metabolites which fish have evolved the ability to detect because of their intrinsic meaning ('spying')? Here we review hormonal pheromone function in fish and then describe a study of the goldfish which tests whether hormonal pheromones are specialized communicatory signals by comparing the profile of steroids released by goldfish with their olfactory responsiveness to these compounds. Little correlation between signal production and detection was found and we conclude that the goldfish hormonal pheromone system most likely exemplifies spying.

In vitro synthesis of 20α-reduced and of 11- and 21-oxygenated steroids and their sulfates by testes of the goldfish (Carassius auratus): Testicular synthesis of corticosteroids

Testes from spermiating goldfish were incubated with [(3)H]17-hydroxyprogesterone. The major products in the unconjugated fraction were identified as androstenedione, androstenetrione, 11-β-hydroxyandrostenedione, 11-ketotestosterone, 17,20α-dihydroxy-4-pregnen-3-one (17,20αP) and 11-deoxycortisol. Testosterone was present predominantly in the glucuronide fraction, but yields were low (1-3%). The major components of the sulfate fraction were 17,20αP and 11-deoxycortisol. The identification of cortisone in low yield (< 2.5010) in both the free and sulfate fractions is the first report of corticosteroid biosynthesis by a teleost testis. The high yields of 17,20αP and 11-deoxycortisol and their sulphates suggests that their possible role in spermiation of the goldfish should be further investigated.

In vitro biosynthesis of steroids, including 11-deoxycortisol and 5 alpha-pregnane-3 beta,7 alpha,17,20 beta-tetrol, by ovaries of the goldfish Carassius auratus during the stage of oocyte final maturation

To examine the production of steroids with potential oocyte maturation-inducing or pheromonal activity in the goldfish (Carassius auratus) we have incubated mature ovaries of this species with 17-[3H]hydroxyprogesterone. The metabolites in the unconjugated, glucuronide, and sulfate fractions were identified by chromatography, microchemical reaction, and, in most cases, crystallization to constant specific activity. A major metabolite, present in all three fractions, was tentatively identified as 5 alpha-pregnane-3 beta,7 alpha,17,20 beta-tetrol. Although 17,20 beta-dihydroxy-4-pregnen-3-one (17,20 beta-P) was found in only low yield (as a sulfate), the presence of the tetrol indicates that it is synthesized in high yield but very rapidly metabolized. The relative proportions of 17,20 alpha-dihydroxy-4-pregnen-3-one (17,20 alpha-P), 11-deoxycortisol (17,21-dihydroxy-4-pregnen-3,20-dione) and 17,20 beta,21-trihydroxy-4-pregnen-3-one (17,20 beta,21-P) varied significantly between incubations and may be affected by the maturational state of the ovary or the method used to stimulate oocyte maturation. Testosterone was present predominantly as its glucuronide. Significant production of glucuronides and sulfates was observed in all incubations. Twenty-five to 30% of the radioactivity remained associated with the tissue, but the distribution of activity between the metabolites did not differ greatly from that found in the medium. These results indicate that 11-deoxycortisol and its 20 beta-reduced derivative (17,20 beta,21-P) may be significant in spawning female goldfish.

17 alpha,20 beta-dihydroxy-4-pregnen-3-one 20-sulphate: a major new metabolite of the teleost oocyte maturation-inducing steroid

This paper describes the discovery of 17 alpha,20 beta-dihydroxy-4-pregnen-3-one 20-sulphate (17,20 beta-P-sulphate) in urine of male and female plaice Pleuronectes platessa, in female Atlantic salmon Salmo salar and in female Dover sole Solea solea. 17 alpha,20 beta-dihydroxy-4-pregnen-3-one (17,20 beta-P) induces oocyte final maturation in teleosts and, whereas levels of the free steroid in maturing/ovulating female plaice are generally less than 1 ng ml-1 and poorly associated with the stage of maturation, the levels of 17,20 beta-P-sulphate are around 1500 ng ml-1 urine, 11 ng ml-1 blood plasma and six-fold higher in maturing than in nonmaturing fish. There are also high levels in spermiating male plaice (ca. 2300 ng ml-1 urine and 20 ng ml-1 blood plasma). 17,20 beta-P-sulphate cannot be hydrolysed by snail (Helix pomatia) sulphatase, but can be completely solvolysed by treatment with trifluoroacetic acid (TFA)/ethyl acetate (1/100, v/v) at 45 degrees for 18 hr. A number of other sulphated steroids have been identified in plaice urine: cortisol, 11-deoxycortisol and 3 alpha,17 alpha,21-trihydroxy-5 beta-pregnan-20-one (which can all be hydrolysed by snail juice); 17 alpha,20 alpha-dihydroxy-4-pregnen-3-one and 17 alpha,20 beta,21-trihydroxy-4-pregnen-3-one (which can both be solvolysed by TFA/ethyl acetate).

Levels of 17 alpha,20 alpha-dihydroxy-4-pregnen-3-one, 3 beta,17 alpha,20 alpha-trihydroxy-5 beta-pregnane, and other sex steroids, in blood plasma of male dab, Limanda limanda (marine flatfish) injected with human chorionic gonadotrophin

In a previous study, plasma sex steroid levels were measured in female dab (Limanda limanda) induced to ovulate by injections of human chorionic gonadotrophin (HCG). In the present study, a similar experiment was carried out on male dabs. In common with female dabs, 17 alpha,20 alpha-dihydroxy-4-pregnen-3-one and 3 beta,17 alpha,20 alpha-trihydroxy-5 beta-pregnane showed the greatest response. Their plasma levels increased, respectively, from 6 +/- 1.6 and 13 +/- 6.2 ng/ml to ca. 62 ng/ml within 36 hr and then decreased. Levels of both steroids remained low in fish injected with saline. There was no statistically significant effect of HCG on plasma testosterone or 11-ketotestosterone concentrations. Initial levels of both hormones were between 10 and 20 ng/ml, and decreased simultaneously in both HCG- and saline-injected fish. Levels of 17 alpha-hydroxy-4-pregnen-3,20-dione, 17 alpha,20 beta-dihydroxy-4-pregnen-3-one, 11-deoxycortisol, and 17 alpha,20 beta, 21-trihydroxy-4-pregnen-3-one were mostly below the detection limits of the assays (0.4 ng/ml). There was no statistically significant effect of HCG on either the total volume of milt collected or the proportion occupied by spermatozoa.

Plasma levels of ovarian steroids, including 17 alpha,21-dihydroxy-4-pregnene-3,20-dione and 3 alpha,17 alpha,21-trihydroxy-5 beta-pregnan-20-one, in female plaice (Pleuronectes platessa) induced to mature with human chorionic gonadotrophin

In one previous paper we reported on the identification of 11-deoxycortisol and 3 alpha,17 alpha,21-trihydroxy-5 beta-pregnan-20-one in the ovaries and plasma of mature female plaice and also described the development of radioimmunoassays for these two steroids. The present paper describes temporal changes in plasma levels of the free and conjugated forms of these and of some other steroids (17 alpha,20 beta-dihydroxy-4-pregnen-3-one, 17 alpha,20 beta,21-trihydroxy-4-pregnen-3-one, 17 alpha,20 alpha-dihydroxy-4-pregnen-3-one, 17 alpha-hydroxy-4-pregnen-3-one, testosterone, and 17 beta-oestradiol) in female plaice injected with and without human chorionic gonadotrophin (HCG). Oocyte final maturation, but not ovulation, was induced by HCG injections. Levels of most of the steroids were also elevated by the HCG injections and were significantly higher than in control fish throughout the experiment (112 hr). The two most abundant steroids were 11-deoxycortisol and 3 alpha,17 alpha,21-trihydroxy-5 beta-pregnan-20-one (up to 600 ng ml-1). Only relatively small amounts of 17 alpha-hydroxy-4-pregnen-3,20-dione (less than 15 ng ml-1), 17 alpha,20 beta-dihydroxy-4-pregnen-3-one, and 17 alpha,20 alpha-dihydroxy-4-pregnen-3-one (less than 5 ng ml-1) were found. 17 alpha,20 beta,21-Trihydroxy-4-pregnen-3-one was not present. Testosterone and 17 beta-oestradiol levels rose briefly, in response to the first of the two HCG injections, and then fell significantly. The ratio of conjugated to free steroids (except for 17 alpha-hydroxy-4-pregnene-3,20-dione and 17 beta-oestradiol) was almost always greater than 1. In the HCG-injected fish, there was a significant negative correlation between the response of 17 beta-oestradiol levels and the response of 11-deoxycortisol and 3 alpha,17 alpha,21-trihydroxy-5 beta-pregnan-20-one levels. This further confirms that, as teleosts approach the time of full maturity, there is switch-over in the ovaries from predominantly C19 and C18 steroid production to predominantly C21 steroid production.

Identification of, and development of radioimmunoassays for 17 alpha, 21-dihydroxy-4-pregnene-3,20-dione and 3 alpha,17 alpha, 21-trihydroxy-5 beta-pregnan-20-one in the ovaries of mature plaice (Pleuronectes platessa)

Ovaries from a female plaice (Pleuronectes platessa) that had been injected with human chorionic gonadotrophin were incubated in vitro with 17 alpha-hydroxy[1,2,6,7-3H]progesterone. The major steroids produced by the ovaries were tentatively identified as 17 alpha,21-dihydroxy-4-pregnene-3,20di-one (11-deoxycortisol; 17,21-P), 17 alpha,21-dihydroxy-5 beta-pregnane-3,20-dione (3 alpha, 17,21-P-5 beta). A high proportion of these steroids was found in a conjugated form (sulphates or glucuronides). Radioimmunoassays were developed for 11-deoxycortisol and for 3 alpha,17,21-P-5 beta and were applied to fractions of mature male and female plaice plasmas and plaice ovarian incubates that had been separated on thin-layer chromatography. The presence of all three steroids, in vivo and in vitro, was confirmed. Particularly high amounts of conjugated 3 alpha,17,21-P-5 beta were found in the plasma of mature females (200-400 ng ml-1). The 3 alpha,17,21-P-5 beta radioimmunoassay also identified 3 alpha,17 alpha-dihydroxy-5 beta-pregnane-20-dione in all three fluids, despite the fact that this steroid was not among the radioactive incubation products of the ovary. These findings are compared with those from another flatfish, the dab (Limanda limanda), where the major gonadal steroids have been shown to be 17 alpha,20 alpha-dihydroxy-4-pregnen-3-one and its 5 beta-pregnane (3-keto and 3 beta-hydroxyl) metabolites.

Radioimmunoassay of ovarian steroids in plasmas of ovulating female sea bass (Dicentrarchus labrax)

Radioimmunoassays of the free and conjugated fractions of plasmas from ovulating sea bass (Dicentrarchus labrax) have revealed the presence of several unusual polar steroids. Among them is 3 alpha,17 alpha,20 beta,21-tetrahydroxy-5 beta-pregnane.

Plasma levels of ovarian steroids, including 17 alpha-20 alpha-dihydroxy-4-pregnen-3-one and 3 beta,17 alpha,20 alpha-trihydroxy-5 beta-pregnane, in female dabs (Limanda limanda)--marine flatfish--induced to mature and ovulate with human chorionic gonadotrophin

Human chorionic gonadotrophin (HCG) effectively stimulated oocyte final maturation and ovulation in female dabs (Limanda limanda) within 5 days of injection, and this was accompanied by significant changes in blood plasma steroid levels. The steroids which showed the greatest responses to the HCG injections were the ones previously found to be the major products of the ovaries in vitro: 17 alpha-20 alpha-dihydroxy-4-pregnen-3-one (17,20 alpha-P) and 3 beta,17 alpha,20 alpha-trihydroxy-5 beta-pregnane (3 beta,17,20 alpha-P-5 beta). 17,20 alpha-P responded more rapidly with peak levels after 32 hr of injection (115 ng ml-1), but 3 beta,17,20 alpha-P-5 beta reached higher levels ca. 12 hr later (320 ng ml-1). Levels of both steroids were not significantly different from initial values by the time of ovulation. 17 alpha,20 beta-Dihydroxy-4-pregnen-3-one, which is likely to be the oocyte maturation-inducing steroid (MIS) in the dab, showed a significant but very variable rise in levels (between 1 and 10 ng ml-1 in individual fish). 17 alpha-Hydroxy-4-pregnene-3,20-dione levels peaked at 6 ng ml-1 between 30 and 36 hr after HCG injection. Of the other C21 steroids identified in the ovaries of teleosts, 17 alpha,20 beta-21-trihydroxy-4-pregnen-3-one could not be detected, and 17 alpha,21-dihydroxy-4-pregnene-3,20-dione (11-deoxycortisol) showed nonsignificant changes compared to the saline-injected controls. HCG caused a decrease in estradiol-17 beta levels within 24 hr, but levels then rose again to a maximum of 8.2 ng ml-1 at ovulation time, possibly caused by the presence of vitellogenic oocytes in the ovaries. Changes in testosterone levels, however, were not significantly different between HCG- and saline-injected females. The role of HCG-responsive C21 steroids in the dab is discussed.

Effects of steroids and human chorionic gonadotrophin on in vitro oocyte final maturation in two marine flatfish: the dab, Limanda limanda, and the plaice, Pleuronectes platessa

This study investigated the role of gonadotrophin and steroids in the induction of in vitro oocyte maturation in dab (Limanda limanda) and plaice (Pleuronectes platessa), two marine flatfish (Pleuronectiformes) in which the oocytes mature and ovulate in groups (or batches). Clusters of folliculated oocytes were incubated for 3 days with a range of doses of either human chorionic gonadotrophin (HCG) or synthetic steroids with a wide range of structures. They were also incubated with extracts from cultures of HCG-stimulated ovaries. Oocytes were always more responsive to HCG than to steroids, and the median efficient doses obtained with HCG were negatively correlated with oocyte diameters. Bioassay sensitivity to steroids was low when compared with other teleosts, and intraassay variability was high, particularly in plaice. Despite the high variability, a common pattern in specificities to steroids was obtained for the two species, which was also similar to other teleost species. Among the most effective steroids found were 17 alpha,20 beta-dihydroxy-4-pregnen-3-one and 17 alpha,20 beta,21-trihydroxy-4-pregnen-3-one. Extracts from incubates were ineffective. The significance of these findings and possible ways to reduce assay variability and improve sensitivity are discussed.

Conjugates of ovarian steroids, including 17 alpha,20 beta-dihydroxy-4-pregnen-3-one (maturation-inducing steroid), accumulate in the urine of a marine teleost (plaice; Pleuronectes platessa)

Free and conjugated 17 alpha,20 beta-dihydroxy-4-pregnen-3-one (17,20 beta-P), 17 alpha,21-dihydroxy-4-pregnene-3,20-dione (11-deoxycortisol) and 3 alpha,17 alpha,21-trihydroxy-5 beta-pregnan-20-one (3 alpha,17,21-P-5 beta) were measured by radioimmunoassay in matching blood plasma and urine samples from plaice (Pleuronectes platessa) females at several ovarian maturity stages: post-vitellogenesis (IV), final oocyte maturation (V), and ovulation (VI). Free steroids were generally low in all samples. Conjugated steroids were up to 2 orders of magnitude higher in urine than in plasma samples. Conjugated 17,20 beta-P was higher in stage V than in stage IV or VI females. Conjugated 11-deoxycortisol was higher in stage IV and V females. Conjugated 3 alpha,17,21-P-5 beta was higher in stage V and VI females. These results support earlier studies which indicated that 17,20 beta-P was the most likely maturation-inducing steroid (MIS) in plaice, and that the urine might be a vehicle for steroid pheromones synthesized by the gonads.

Synthesis of 20 alpha-hydroxylated steroids by ovaries of the dab (Limanda limanda)

Dab (Limanda limanda) ovarian fragments were incubated in vitro with either [4,7-3H]pregnenolone or 17 alpha-hydroxy[1,2,6,7-3H]progesterone to investigate the pattern of steroidogenesis. A major enzyme found in the dab ovary was 20 alpha-hydroxysteroid dehydrogenase. Among the steroids that were tentatively identified in ovarian incubates were 17 alpha,20 alpha-dihydroxy-4-pregnen-3-one (17,20 alpha-P). 17 alpha,20 alpha-dihydroxy-5 beta-pregnan-3-one, 3 beta, 17 alpha,20 alpha-trihydroxy-5 beta-pregnane (3 beta,17,20 alpha-P-5 beta), and 3 alpha,17 alpha,20 alpha-trihydroxy-5 beta-pregnane. The presence of these steroids in plasma of mature female and male dabs was studied by radioimmunoassay. The antiserum was raised against 17,20 alpha-P. The 17,20 alpha-[3H]P label was produced by incubating place milt with 17 alpha-hydroxy [3H]progesterone. The radioimmunoassay was shown to have a high cross-reaction with the 5 beta-reduced analogues of 17,20 alpha-P and was therefore used, in conjunction with thin-layer chromatography, to measure the steroids. High concentrations of both 17,20 alpha-P and 3 beta,17,20 alpha-P-5 beta found in female and male dab plasma. The possible role of these steroids is discussed.

Seasonal variations in plasma and pituitary levels of gonadotrophin in males and females of two strains of rainbow trout (Salmo gairdneri)

Male and female rainbow trout of an autumn- and a winter-spawning strain were sampled every 28 days over a period of 2 years, starting when they were approximately 6 months old. Plasma and pituitary levels of gonadotrophin (GTH) were measured by a radioimmunoassay that preferentially detected the gonadotrophin referred to as either GTH II or "maturational and ovulatory" GTH. The general pattern of gonadal development and the profile of GTH in plasma and pituitary were similar in the two strains, except that the timing was different. Gonadal development in both sexes began about 9 months before spawning, concomitant with an increase in pituitary GTH content. In both sexes, pituitary GTH levels rose dramatically by about 50,000-fold, peaking at the beginning of spawning. They remained high many months thereafter, before falling slowly. Plasma GTH levels during the reproductive cycle were different in the two sexes. In both sexes plasma GTH levels remained very low and unchanged until shortly before full sexual maturity was reached. GTH levels then rose only slightly in males, but markedly in females. The slightly elevated GTH levels persisted many months in males, throughout the period when they could be stripped of milt, but in females they were elevated only a short time around ovulation. These results suggest that although a GTH II-like gonadotrophin is present in the pituitary gland throughout the period of gonadal growth, it does not appear to be released in any substantial amounts into the blood until near spawning.